B 1. Field of the Invention
This invention relates in general to air conditioning systems and more particularly to a mechanism which utilizes evaporatively cooled air for improving the operating efficiency of a refrigeration unit.
2. Description of the Prior Art
For many years residential and business establishments in warm, arid and semi-arid climates were cooled almost exclusively by evaporative cooling. As is well known, evaporative coolers are relatively low cost devices, both from initial cost and operating cost standpoints, and are very effective at times of relatively low humidity and become less effective as the humidity increases.
Due to the lessening of cooling effectiveness in times of relatively high humidity, many existing evaporative coolers were replaced with refrigeration units when such units were developed in suitable packages and at reasonable initial costs, and new construction went almost exclusively to the use of refrigeration units. This trend, away from evaporative coolers to refrigeration units, started about 20 to 25 years ago and was very well accepted by the consuming public as long as energy was plentiful and relatively inexpensive.
Now, however, with energy in relatively short supply and with the escalating energy costs, many are looking once again to the evaporative cooler for a source of economic relief. The trend today is not a complete reversal of the movement away from evaporative coolers, but is toward a compatible union of evaporative coolers and refrigeration units.
To establish a compatible union, most consumers are placing both an evaporative cooler and a refrigeration unit in communication with a common air delivery ducting network, and using the evaporative cooler when climatic conditions allow the effective use thereof and use the refrigeration unit only when necessary.
A typical installation of this type usually includes a riser duct leading from the air distribution ducting network to the refrigeration unit and a separate riser duct leading to the evaporative cooler, with each of those riser ducts having some sort of damper mechanism mounted therein. When the refrigeration unit is being used, the damper in its riser duct is, of course, open and the damper in the riser duct leading to the evaporative cooler is closed, and when the evaporative cooler is being used the damper positions are reversed.
This combined usage of evaporative coolers and refrigeration units is proving to be very successful and such combination systems are being installed in ever increasing numbers. However, it is believed that such systems could be more effectively used by adapting the system so that the relatively inexpensively operated evaporative cooler could be utilized to reduce the building heat load and to increase the operating efficiency of the refrigeration unit when it is being operated to cool the living space of the building.
It has long been known that the heat buildup in attic spaces above an area that is being cooled can have a considerable effect on the heat load of the cooled area. For example, in the attic space of a single story building located in a warm climate such as the Southwestern part of the United States, attic temperatures of 120.degree. F. to 150.degree. F. are not uncommon in the summertime. If the area being cooled is kept at about 80.degree. F. this means that a temperature differential of from about 40.degree. F. to 70.degree. F. is felt across the ceiling. In the absence of insulation, the ceiling becomes in effect, a radiant heater shortly after the sun comes up and remains that way until well after sunset. Even with proper attic insulation, the flow of heat from the attic into the living area is not completely stopped but is merely reduced in intensity and slowed down in that the heat in the attic space will increase the temperature of the insulation during the daytime and when the sun goes down the heated insulation will radiate heat into the living area well into the nighttime hours. From this it will be seen that the heat buildup in attic spaces places a considerable heat load on the air conditioning unit being used to cool the living space. It has been estimated that in a typical single story building, about one third of the heat load comes from the ceiling.
Recently, a very effective means has been suggested for more efficient usage of the combined air conditioning systems of the above described type, and this means is fully disclosed in U.S. patent application Ser. No. 146,663 filed on May 5, 1980, for an "Air Diversion Duct" by Mark N. Worthington. Briefly, the air diversion duct of the above referenced U.S. patent application is a two-position device which is mounted in the riser duct leading from the evaporative cooler to the building's air distribution ducting network. When the combination air conditioning system is in its evaporative cooling mode, the air diversion duct is positioned to supply evaporatively cooled air directly to the air distribution ducting network in the customary manner. When the combination air conditioning system is in its refrigeration mode, the air diversion duct is placed in its second position which isolates the evaporative cooler from the building's air distribution ducting network and opens auxiliary air outlets which are in communication with the building's attic space. In this manner, the evaporative cooler may be operated to supply the evaporatively cooled air to the building's attic space and thereby help to reduce the overall heat load on the building.
The air diversion duct of the above referenced U.S. patent application adds considerable versatility and efficiency to the known combination air conditioning system. However, it is believed that the combination air conditioning system can be further enhanced by addition of a mechanism which increases the efficiency of the refrigeration unit while it is being operated to cool the living space of the building.
As is well known, the condenser coil of a refrigeration unit, either of the conventional type or a heat pump, must be cooled for proper operation of the refrigeration unit. Some refrigeration systems are liquid cooled but these are usually very large commercial units. The most commonly used system for radiating the heat of condensation into the atmosphere is accomplished by drawing atmospheric air across the condenser coil by means of a power operated fan, and then exhausting the air back into the atmosphere. Cooling of the condenser coil by air is relatively efficient as long as the temperature of the atmospheric air is low, i.e., does not exceed for example, 90.degree. F. to 95.degree. F. Unfortunately, when a refrigeration unit is needed most, atmospheric air temperatures are usually above the point at which condenser cooling is efficiently accomplished, and ambient temperatures within the refrigeration unit can be considerably above atmospheric air temperature. When the atmospheric air temperature is, for example, 110.degree. F., the temperature within the unit itself, in which the condenser and compressor are housed, may be as high as 140.degree. F. or even 150.degree. F. depending on the location of the refrigeration unit. This relatively higher temperature of the ambient air is due to absorption of heat from the sun as well as the generation of heat due to the work being performed by the refrigeration unit.
As atmospheric and ambient temperatures increase, the condenser coil cooling efficiency drops and when this occurs, the head pressure against which the refrigeration unit compressor is operating increases. When the head pressure increases, the compressor operates longer and draws more amperage. This, of course, results in increased operating costs with decreased unit longevity.
This problem has long been recognized and attempts have been made over the years to find an efficient low cost way of keeping the temperature of the air used in cooling the condenser coil at a temperature at which such cooling is efficiently accomplished.
A particular prior art attempt to enhance the air cooling of the condenser coil of a refrigeration unit is disclosed in U.S. Pat. No. 3,108,451 issued on Oct. 29, 1963 to A. E. Clifford. In the Clifford structure, a porous pad of the type commonly used in evaporative coolers is positioned in the air path leading to the condenser coil. The pad is wetted with water so that the air moving toward the coil through the pad is cooled by evaporation. In this coil cooling arrangement, and the many variations thereof tried throughout the years, two problems have kept such mechanisms from achieving any significant degree of commercial success.
The first problem with these prior art coil cooling arrangements results from free moisture carried by the evaporatively cooled air. The free moisture is deposited on the condenser coil and on other components within the refrigeration unit, and such deposition causes scaling and corrosion which decreases the heat radiating capabilities of the condenser coil in particular and other unit components in general. In a surprisingly short time, the scaling and corrosion will ruin those components.
The second problem with this prior art coil cooling arrangement is restricted airflow to the condenser coil. The wetted pad will restrict airflow to the coil somewhat, but, this alone will not present any problem as long as the wet pad is clean. However, mineral deposition, or scaling, of the pad is an inherent problem along with trapped airborne matter such as dirt. Due to the nature of the pads, it is not practical to clean them, thus, periodic replacement is required. As is all too often the case, the time between pad replacements is often extended beyond what it should be and in some cases is ignored entirely. When this occurs, the prior art coil cooling arrangement compounds the problem rather than alleviating it.
To the best of my knowledge, no devices or mechanisms have been devised or suggested to provide a combination air conditioning system of the above described type with the capabilities of increasing the operating efficiency of its refrigeration unit.